package com.miemie;

import java.util.Scanner;

public class FrogJump {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()) {
            int n = scanner.nextInt();
            System.out.println(dp(n));
        }
    }

    public static int dp(int n) {
        int f0 = 1;
        int f1 = 2;
        if(n == 1){
            return 1;
        }
        if(n == 2) {
            return 2;
        }
        int f = 0;
        for (int i = 3; i <= n; i++) {
            f = f0 + f1;
            f0 = f1;
            f1 = f;
        }
        return f;
    }
}
